1. Field of the Invention
The present invention relates generally to the Internet Small Computer Systems Interface (iSCSI), and more particularly to a method of improving iSCSI data transfers.
2. Description of Related Art
The iSCSI protocol carries SCSI (Small Computer Systems Interface) commands over a commonly used IP network by encapsulating SCSI commands into TCP/IP (Transmission Control Protocol/Internet Protocol) Internet protocol packets and supporting block-based data transmission using the IP network. The ubiquity of IP networks, including the Internet, local area networks (LANs) and wide area networks (WANs), helps the adoption of the iSCSI protocol, since iSCSI can run on existing networks and no significant investment in infrastructure is required. On the other hand, sharing the network infrastructure with general network traffic may result in latency: the time required for commands and data to travel between an iSCSI initiator (i.e., an iSCSI client), and an Internet Storage Name Service (iSNS) server and an iSCSI target (i.e., an iSCSI server, which is a storage device). When data transfers involve several request and response transactions, the latency may cause low iSCSI performance which may impede further iSCSI developments.
One approach to reduce the latency is to use an iSCSI-aware switch which gives priority to iSCSI traffic that is flowing between iSCSI initiators and iSCSI targets. An iSCSI-aware switch needs to listen to the traffic destined to an iSCSI target port in order to identify iSCSI sessions. When an iSCSI session is identified, its related traffic may be given priority over other network traffic flowing through the switch. The iSCSI target port is a piece of information an iSCSI initiator may receive from an iSNS server, and is an application logical port, e.g., a TCP or UDP (User Datagram Protocol) logical port.
However, switches on the communication path between an iSCSI initiator and an iSCSI target may not be on the communication path between the iSCSI initiator and an iSNS server, and consequently may miss information about the iSCSI target port and fail to identify an iSCSI session.
Therefore, it may be desirable to provide a method to distinguish and prioritize iSCSI traffic in an IP network.